PeerStreamer

/**

 * FLAC audio encoder

 * Copyright (c) 2006  Justin Ruggles <justin.ruggles@gmail.com>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "libavutil/crc.h"

#include "libavutil/md5.h"

#include "avcodec.h"

#include "get_bits.h"

#include "golomb.h"

#include "lpc.h"

#include "flac.h"

#include "flacdata.h"

#define FLAC_SUBFRAME_CONSTANT  0

#define FLAC_SUBFRAME_VERBATIM  1

#define FLAC_SUBFRAME_FIXED     8

#define FLAC_SUBFRAME_LPC      32

#define MAX_FIXED_ORDER     4

#define MAX_PARTITION_ORDER 8

#define MAX_PARTITIONS     (1 << MAX_PARTITION_ORDER)

#define MAX_LPC_PRECISION  15

#define MAX_LPC_SHIFT      15

#define MAX_RICE_PARAM     14

typedef struct CompressionOptions {

    int compression_level;

    int block_time_ms;

    enum AVLPCType lpc_type;

    int lpc_passes;

    int lpc_coeff_precision;

    int min_prediction_order;

    int max_prediction_order;

    int prediction_order_method;

    int min_partition_order;

    int max_partition_order;

} CompressionOptions;

typedef struct RiceContext {

    int porder;

    int params[MAX_PARTITIONS];

} RiceContext;

typedef struct FlacSubframe {

    int type;

    int type_code;

    int obits;

    int order;

    int32_t coefs[MAX_LPC_ORDER];

    int shift;

    RiceContext rc;

    int32_t samples[FLAC_MAX_BLOCKSIZE];

    int32_t residual[FLAC_MAX_BLOCKSIZE+1];

} FlacSubframe;

typedef struct FlacFrame {

    FlacSubframe subframes[FLAC_MAX_CHANNELS];

    int blocksize;

    int bs_code[2];

    uint8_t crc8;

    int ch_mode;

    int verbatim_only;

} FlacFrame;

typedef struct FlacEncodeContext {

    PutBitContext pb;

    int channels;

    int samplerate;

    int sr_code[2];

    int max_blocksize;

    int min_framesize;

    int max_framesize;

    int max_encoded_framesize;

    uint32_t frame_count;

    uint64_t sample_count;

    uint8_t md5sum[16];

    FlacFrame frame;

    CompressionOptions options;

    AVCodecContext *avctx;

    LPCContext lpc_ctx;

    struct AVMD5 *md5ctx;

} FlacEncodeContext;

/**

 * Write streaminfo metadata block to byte array.

 */

static void write_streaminfo(FlacEncodeContext *s, uint8_t *header)

{

    PutBitContext pb;

    memset(header, 0, FLAC_STREAMINFO_SIZE);

    init_put_bits(&pb, header, FLAC_STREAMINFO_SIZE);

    /* streaminfo metadata block */

    put_bits(&pb, 16, s->max_blocksize);

    put_bits(&pb, 16, s->max_blocksize);

    put_bits(&pb, 24, s->min_framesize);

    put_bits(&pb, 24, s->max_framesize);

    put_bits(&pb, 20, s->samplerate);

    put_bits(&pb, 3, s->channels-1);

    put_bits(&pb, 5, 15);       /* bits per sample - 1 */

    /* write 36-bit sample count in 2 put_bits() calls */

    put_bits(&pb, 24, (s->sample_count & 0xFFFFFF000LL) >> 12);

    put_bits(&pb, 12,  s->sample_count & 0x000000FFFLL);

    flush_put_bits(&pb);

    memcpy(&header[18], s->md5sum, 16);

}

/**

 * Set blocksize based on samplerate.

 * Choose the closest predefined blocksize >= BLOCK_TIME_MS milliseconds.

 */

static int select_blocksize(int samplerate, int block_time_ms)

{

    int i;

    int target;

    int blocksize;

    assert(samplerate > 0);

    blocksize = ff_flac_blocksize_table[1];

    target    = (samplerate * block_time_ms) / 1000;

    for (i = 0; i < 16; i++) {

        if (target >= ff_flac_blocksize_table[i] &&

            ff_flac_blocksize_table[i] > blocksize) {

            blocksize = ff_flac_blocksize_table[i];

        }

    }

    return blocksize;

}

static av_cold void dprint_compression_options(FlacEncodeContext *s)

{

    AVCodecContext     *avctx = s->avctx;

    CompressionOptions *opt   = &s->options;

    av_log(avctx, AV_LOG_DEBUG, " compression: %d\n", opt->compression_level);

    switch (opt->lpc_type) {

    case AV_LPC_TYPE_NONE:

        av_log(avctx, AV_LOG_DEBUG, " lpc type: None\n");

        break;

    case AV_LPC_TYPE_FIXED:

        av_log(avctx, AV_LOG_DEBUG, " lpc type: Fixed pre-defined coefficients\n");

        break;

    case AV_LPC_TYPE_LEVINSON:

        av_log(avctx, AV_LOG_DEBUG, " lpc type: Levinson-Durbin recursion with Welch window\n");

        break;

    case AV_LPC_TYPE_CHOLESKY:

        av_log(avctx, AV_LOG_DEBUG, " lpc type: Cholesky factorization, %d pass%s\n",

               opt->lpc_passes, opt->lpc_passes == 1 ? "" : "es");

        break;

    }

    av_log(avctx, AV_LOG_DEBUG, " prediction order: %d, %d\n",

           opt->min_prediction_order, opt->max_prediction_order);

    switch (opt->prediction_order_method) {

    case ORDER_METHOD_EST:

        av_log(avctx, AV_LOG_DEBUG, " order method: %s\n", "estimate");

        break;

    case ORDER_METHOD_2LEVEL:

        av_log(avctx, AV_LOG_DEBUG, " order method: %s\n", "2-level");

        break;

    case ORDER_METHOD_4LEVEL:

        av_log(avctx, AV_LOG_DEBUG, " order method: %s\n", "4-level");

        break;

    case ORDER_METHOD_8LEVEL:

        av_log(avctx, AV_LOG_DEBUG, " order method: %s\n", "8-level");

        break;

    case ORDER_METHOD_SEARCH:

        av_log(avctx, AV_LOG_DEBUG, " order method: %s\n", "full search");

        break;

    case ORDER_METHOD_LOG:

        av_log(avctx, AV_LOG_DEBUG, " order method: %s\n", "log search");

        break;

    }

    av_log(avctx, AV_LOG_DEBUG, " partition order: %d, %d\n",

           opt->min_partition_order, opt->max_partition_order);

    av_log(avctx, AV_LOG_DEBUG, " block size: %d\n", avctx->frame_size);

    av_log(avctx, AV_LOG_DEBUG, " lpc precision: %d\n",

           opt->lpc_coeff_precision);

}

static av_cold int flac_encode_init(AVCodecContext *avctx)

{

    int freq = avctx->sample_rate;

    int channels = avctx->channels;

    FlacEncodeContext *s = avctx->priv_data;

    int i, level, ret;

    uint8_t *streaminfo;

    s->avctx = avctx;

    if (avctx->sample_fmt != AV_SAMPLE_FMT_S16)

        return -1;

    if (channels < 1 || channels > FLAC_MAX_CHANNELS)

        return -1;

    s->channels = channels;

    /* find samplerate in table */

    if (freq < 1)

        return -1;

    for (i = 4; i < 12; i++) {

        if (freq == ff_flac_sample_rate_table[i]) {

            s->samplerate = ff_flac_sample_rate_table[i];

            s->sr_code[0] = i;

            s->sr_code[1] = 0;

            break;

        }

    }

    /* if not in table, samplerate is non-standard */

    if (i == 12) {

        if (freq % 1000 == 0 && freq < 255000) {

            s->sr_code[0] = 12;

            s->sr_code[1] = freq / 1000;

        } else if (freq % 10 == 0 && freq < 655350) {

            s->sr_code[0] = 14;

            s->sr_code[1] = freq / 10;

        } else if (freq < 65535) {

            s->sr_code[0] = 13;

            s->sr_code[1] = freq;

        } else {

            return -1;

        }

        s->samplerate = freq;

    }

    /* set compression option defaults based on avctx->compression_level */

    if (avctx->compression_level < 0)

        s->options.compression_level = 5;

    else

        s->options.compression_level = avctx->compression_level;

    level = s->options.compression_level;

    if (level > 12) {

        av_log(avctx, AV_LOG_ERROR, "invalid compression level: %d\n",

               s->options.compression_level);

        return -1;

    }

    s->options.block_time_ms = ((int[]){ 27, 27, 27,105,105,105,105,105,105,105,105,105,105})[level];

    s->options.lpc_type      = ((int[]){ AV_LPC_TYPE_FIXED,    AV_LPC_TYPE_FIXED,    AV_LPC_TYPE_FIXED,

                                         AV_LPC_TYPE_LEVINSON, AV_LPC_TYPE_LEVINSON, AV_LPC_TYPE_LEVINSON,

                                         AV_LPC_TYPE_LEVINSON, AV_LPC_TYPE_LEVINSON, AV_LPC_TYPE_LEVINSON,

                                         AV_LPC_TYPE_LEVINSON, AV_LPC_TYPE_LEVINSON, AV_LPC_TYPE_LEVINSON,

                                         AV_LPC_TYPE_LEVINSON})[level];

    s->options.min_prediction_order = ((int[]){  2,  0,  0,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1})[level];

    s->options.max_prediction_order = ((int[]){  3,  4,  4,  6,  8,  8,  8,  8, 12, 12, 12, 32, 32})[level];

    s->options.prediction_order_method = ((int[]){ ORDER_METHOD_EST,    ORDER_METHOD_EST,    ORDER_METHOD_EST,

                                                   ORDER_METHOD_EST,    ORDER_METHOD_EST,    ORDER_METHOD_EST,

                                                   ORDER_METHOD_4LEVEL, ORDER_METHOD_LOG,    ORDER_METHOD_4LEVEL,

                                                   ORDER_METHOD_LOG,    ORDER_METHOD_SEARCH, ORDER_METHOD_LOG,

                                                   ORDER_METHOD_SEARCH})[level];

    s->options.min_partition_order = ((int[]){  2,  2,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0})[level];

    s->options.max_partition_order = ((int[]){  2,  2,  3,  3,  3,  8,  8,  8,  8,  8,  8,  8,  8})[level];

    /* set compression option overrides from AVCodecContext */

#if FF_API_USE_LPC

    /* for compatibility with deprecated AVCodecContext.use_lpc */

    if (avctx->use_lpc == 0) {

        s->options.lpc_type = AV_LPC_TYPE_FIXED;

    } else if (avctx->use_lpc == 1) {

        s->options.lpc_type = AV_LPC_TYPE_LEVINSON;

    } else if (avctx->use_lpc > 1) {

        s->options.lpc_type   = AV_LPC_TYPE_CHOLESKY;

        s->options.lpc_passes = avctx->use_lpc - 1;

    }

#endif

    if (avctx->lpc_type > AV_LPC_TYPE_DEFAULT) {

        if (avctx->lpc_type > AV_LPC_TYPE_CHOLESKY) {

            av_log(avctx, AV_LOG_ERROR, "unknown lpc type: %d\n", avctx->lpc_type);

            return -1;

        }

        s->options.lpc_type = avctx->lpc_type;

        if (s->options.lpc_type == AV_LPC_TYPE_CHOLESKY) {

            if (avctx->lpc_passes < 0) {

                // default number of passes for Cholesky

                s->options.lpc_passes = 2;

            } else if (avctx->lpc_passes == 0) {

                av_log(avctx, AV_LOG_ERROR, "invalid number of lpc passes: %d\n",

                       avctx->lpc_passes);

                return -1;

            } else {

                s->options.lpc_passes = avctx->lpc_passes;

            }

        }

    }

    if (s->options.lpc_type == AV_LPC_TYPE_NONE) {

        s->options.min_prediction_order = 0;

    } else if (avctx->min_prediction_order >= 0) {

        if (s->options.lpc_type == AV_LPC_TYPE_FIXED) {

            if (avctx->min_prediction_order > MAX_FIXED_ORDER) {

                av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n",

                       avctx->min_prediction_order);

                return -1;

            }

        } else if (avctx->min_prediction_order < MIN_LPC_ORDER ||

                   avctx->min_prediction_order > MAX_LPC_ORDER) {

            av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n",

                   avctx->min_prediction_order);

            return -1;

        }

        s->options.min_prediction_order = avctx->min_prediction_order;

    }

    if (s->options.lpc_type == AV_LPC_TYPE_NONE) {

        s->options.max_prediction_order = 0;

    } else if (avctx->max_prediction_order >= 0) {

        if (s->options.lpc_type == AV_LPC_TYPE_FIXED) {

            if (avctx->max_prediction_order > MAX_FIXED_ORDER) {

                av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n",

                       avctx->max_prediction_order);

                return -1;

            }

        } else if (avctx->max_prediction_order < MIN_LPC_ORDER ||

                   avctx->max_prediction_order > MAX_LPC_ORDER) {

            av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n",

                   avctx->max_prediction_order);

            return -1;

        }

        s->options.max_prediction_order = avctx->max_prediction_order;

    }

    if (s->options.max_prediction_order < s->options.min_prediction_order) {

        av_log(avctx, AV_LOG_ERROR, "invalid prediction orders: min=%d max=%d\n",

               s->options.min_prediction_order, s->options.max_prediction_order);

        return -1;

    }

    if (avctx->prediction_order_method >= 0) {

        if (avctx->prediction_order_method > ORDER_METHOD_LOG) {

            av_log(avctx, AV_LOG_ERROR, "invalid prediction order method: %d\n",

                   avctx->prediction_order_method);

            return -1;

        }

        s->options.prediction_order_method = avctx->prediction_order_method;

    }

    if (avctx->min_partition_order >= 0) {

        if (avctx->min_partition_order > MAX_PARTITION_ORDER) {

            av_log(avctx, AV_LOG_ERROR, "invalid min partition order: %d\n",

                   avctx->min_partition_order);

            return -1;

        }

        s->options.min_partition_order = avctx->min_partition_order;

    }

    if (avctx->max_partition_order >= 0) {

        if (avctx->max_partition_order > MAX_PARTITION_ORDER) {

            av_log(avctx, AV_LOG_ERROR, "invalid max partition order: %d\n",

                   avctx->max_partition_order);

            return -1;

        }

        s->options.max_partition_order = avctx->max_partition_order;

    }

    if (s->options.max_partition_order < s->options.min_partition_order) {

        av_log(avctx, AV_LOG_ERROR, "invalid partition orders: min=%d max=%d\n",

               s->options.min_partition_order, s->options.max_partition_order);

        return -1;

    }

    if (avctx->frame_size > 0) {

        if (avctx->frame_size < FLAC_MIN_BLOCKSIZE ||

                avctx->frame_size > FLAC_MAX_BLOCKSIZE) {

            av_log(avctx, AV_LOG_ERROR, "invalid block size: %d\n",

                   avctx->frame_size);

            return -1;

        }

    } else {

        s->avctx->frame_size = select_blocksize(s->samplerate, s->options.block_time_ms);

    }

    s->max_blocksize = s->avctx->frame_size;

    /* set LPC precision */

    if (avctx->lpc_coeff_precision > 0) {

        if (avctx->lpc_coeff_precision > MAX_LPC_PRECISION) {

            av_log(avctx, AV_LOG_ERROR, "invalid lpc coeff precision: %d\n",

                   avctx->lpc_coeff_precision);

            return -1;

        }

        s->options.lpc_coeff_precision = avctx->lpc_coeff_precision;

    } else {

        /* default LPC precision */

        s->options.lpc_coeff_precision = 15;

    }

    /* set maximum encoded frame size in verbatim mode */

    s->max_framesize = ff_flac_get_max_frame_size(s->avctx->frame_size,

                                                  s->channels, 16);

    /* initialize MD5 context */

    s->md5ctx = av_malloc(av_md5_size);

    if (!s->md5ctx)

        return AVERROR(ENOMEM);

    av_md5_init(s->md5ctx);

    streaminfo = av_malloc(FLAC_STREAMINFO_SIZE);

    if (!streaminfo)

        return AVERROR(ENOMEM);

    write_streaminfo(s, streaminfo);

    avctx->extradata = streaminfo;

    avctx->extradata_size = FLAC_STREAMINFO_SIZE;

    s->frame_count   = 0;

    s->min_framesize = s->max_framesize;

    avctx->coded_frame = avcodec_alloc_frame();

    if (!avctx->coded_frame)

        return AVERROR(ENOMEM);

    ret = ff_lpc_init(&s->lpc_ctx, avctx->frame_size,

                      s->options.max_prediction_order, AV_LPC_TYPE_LEVINSON);

    dprint_compression_options(s);

    return ret;

}

static void init_frame(FlacEncodeContext *s)

{

    int i, ch;

    FlacFrame *frame;

    frame = &s->frame;

    for (i = 0; i < 16; i++) {

        if (s->avctx->frame_size == ff_flac_blocksize_table[i]) {

            frame->blocksize  = ff_flac_blocksize_table[i];

            frame->bs_code[0] = i;

            frame->bs_code[1] = 0;

            break;

        }

    }

    if (i == 16) {

        frame->blocksize = s->avctx->frame_size;

        if (frame->blocksize <= 256) {

            frame->bs_code[0] = 6;

            frame->bs_code[1] = frame->blocksize-1;

        } else {

            frame->bs_code[0] = 7;

            frame->bs_code[1] = frame->blocksize-1;

        }

    }

    for (ch = 0; ch < s->channels; ch++)

        frame->subframes[ch].obits = 16;

    frame->verbatim_only = 0;

}

/**

 * Copy channel-interleaved input samples into separate subframes.

 */

static void copy_samples(FlacEncodeContext *s, const int16_t *samples)

{

    int i, j, ch;

    FlacFrame *frame;

    frame = &s->frame;

    for (i = 0, j = 0; i < frame->blocksize; i++)

        for (ch = 0; ch < s->channels; ch++, j++)

            frame->subframes[ch].samples[i] = samples[j];

}

static int rice_count_exact(int32_t *res, int n, int k)

{

    int i;

    int count = 0;

    for (i = 0; i < n; i++) {

        int32_t v = -2 * res[i] - 1;

        v ^= v >> 31;

        count += (v >> k) + 1 + k;

    }

    return count;

}

static int subframe_count_exact(FlacEncodeContext *s, FlacSubframe *sub,

                                int pred_order)

{

    int p, porder, psize;

    int i, part_end;

    int count = 0;

    /* subframe header */

    count += 8;

    /* subframe */

    if (sub->type == FLAC_SUBFRAME_CONSTANT) {

        count += sub->obits;

    } else if (sub->type == FLAC_SUBFRAME_VERBATIM) {

        count += s->frame.blocksize * sub->obits;

    } else {

        /* warm-up samples */

        count += pred_order * sub->obits;

        /* LPC coefficients */

        if (sub->type == FLAC_SUBFRAME_LPC)

            count += 4 + 5 + pred_order * s->options.lpc_coeff_precision;

        /* rice-encoded block */

        count += 2;

        /* partition order */

        porder = sub->rc.porder;

        psize  = s->frame.blocksize >> porder;

        count += 4;

        /* residual */

        i        = pred_order;

        part_end = psize;

        for (p = 0; p < 1 << porder; p++) {

            int k = sub->rc.params[p];

            count += 4;

            count += rice_count_exact(&sub->residual[i], part_end - i, k);

            i = part_end;

            part_end = FFMIN(s->frame.blocksize, part_end + psize);

        }

    }

    return count;

}

#define rice_encode_count(sum, n, k) (((n)*((k)+1))+((sum-(n>>1))>>(k)))

/**

 * Solve for d/dk(rice_encode_count) = n-((sum-(n>>1))>>(k+1)) = 0.

 */

static int find_optimal_param(uint32_t sum, int n)

{

    int k;

    uint32_t sum2;

    if (sum <= n >> 1)

        return 0;

    sum2 = sum - (n >> 1);

    k    = av_log2(n < 256 ? FASTDIV(sum2, n) : sum2 / n);

    return FFMIN(k, MAX_RICE_PARAM);

}

static uint32_t calc_optimal_rice_params(RiceContext *rc, int porder,

                                         uint32_t *sums, int n, int pred_order)

{

    int i;

    int k, cnt, part;

    uint32_t all_bits;

    part     = (1 << porder);

    all_bits = 4 * part;

    cnt = (n >> porder) - pred_order;

    for (i = 0; i < part; i++) {

        k = find_optimal_param(sums[i], cnt);

        rc->params[i] = k;

        all_bits += rice_encode_count(sums[i], cnt, k);

        cnt = n >> porder;

    }

    rc->porder = porder;

    return all_bits;

}

static void calc_sums(int pmin, int pmax, uint32_t *data, int n, int pred_order,

                      uint32_t sums[][MAX_PARTITIONS])

{

    int i, j;

    int parts;

    uint32_t *res, *res_end;

    /* sums for highest level */

    parts   = (1 << pmax);

    res     = &data[pred_order];

    res_end = &data[n >> pmax];

    for (i = 0; i < parts; i++) {

        uint32_t sum = 0;

        while (res < res_end)

            sum += *(res++);

        sums[pmax][i] = sum;

        res_end += n >> pmax;

    }

    /* sums for lower levels */

    for (i = pmax - 1; i >= pmin; i--) {

        parts = (1 << i);

        for (j = 0; j < parts; j++)

            sums[i][j] = sums[i+1][2*j] + sums[i+1][2*j+1];

    }

}

static uint32_t calc_rice_params(RiceContext *rc, int pmin, int pmax,

                                 int32_t *data, int n, int pred_order)

{

    int i;

    uint32_t bits[MAX_PARTITION_ORDER+1];

    int opt_porder;

    RiceContext tmp_rc;

    uint32_t *udata;

    uint32_t sums[MAX_PARTITION_ORDER+1][MAX_PARTITIONS];

    assert(pmin >= 0 && pmin <= MAX_PARTITION_ORDER);

    assert(pmax >= 0 && pmax <= MAX_PARTITION_ORDER);

    assert(pmin <= pmax);

    udata = av_malloc(n * sizeof(uint32_t));

    for (i = 0; i < n; i++)

        udata[i] = (2*data[i]) ^ (data[i]>>31);

    calc_sums(pmin, pmax, udata, n, pred_order, sums);

    opt_porder = pmin;

    bits[pmin] = UINT32_MAX;

    for (i = pmin; i <= pmax; i++) {

        bits[i] = calc_optimal_rice_params(&tmp_rc, i, sums[i], n, pred_order);

        if (bits[i] <= bits[opt_porder]) {

            opt_porder = i;

            *rc = tmp_rc;

        }

    }

    av_freep(&udata);

    return bits[opt_porder];

}

static int get_max_p_order(int max_porder, int n, int order)

{

    int porder = FFMIN(max_porder, av_log2(n^(n-1)));

    if (order > 0)

        porder = FFMIN(porder, av_log2(n/order));

    return porder;

}

static uint32_t find_subframe_rice_params(FlacEncodeContext *s,

                                          FlacSubframe *sub, int pred_order)

{

    int pmin = get_max_p_order(s->options.min_partition_order,

                               s->frame.blocksize, pred_order);

    int pmax = get_max_p_order(s->options.max_partition_order,

                               s->frame.blocksize, pred_order);

    uint32_t bits = 8 + pred_order * sub->obits + 2 + 4;

    if (sub->type == FLAC_SUBFRAME_LPC)

        bits += 4 + 5 + pred_order * s->options.lpc_coeff_precision;

    bits += calc_rice_params(&sub->rc, pmin, pmax, sub->residual,

                             s->frame.blocksize, pred_order);

    return bits;

}

static void encode_residual_fixed(int32_t *res, const int32_t *smp, int n,

                                  int order)

{

    int i;

    for (i = 0; i < order; i++)

        res[i] = smp[i];

    if (order == 0) {

        for (i = order; i < n; i++)

            res[i] = smp[i];

    } else if (order == 1) {

        for (i = order; i < n; i++)

            res[i] = smp[i] - smp[i-1];

    } else if (order == 2) {

        int a = smp[order-1] - smp[order-2];

        for (i = order; i < n; i += 2) {

            int b    = smp[i  ] - smp[i-1];

            res[i]   = b - a;

            a        = smp[i+1] - smp[i  ];

            res[i+1] = a - b;

        }

    } else if (order == 3) {

        int a = smp[order-1] -   smp[order-2];

        int c = smp[order-1] - 2*smp[order-2] + smp[order-3];

        for (i = order; i < n; i += 2) {

            int b    = smp[i  ] - smp[i-1];

            int d    = b - a;

            res[i]   = d - c;

            a        = smp[i+1] - smp[i  ];

            c        = a - b;

            res[i+1] = c - d;

        }

    } else {

        int a = smp[order-1] -   smp[order-2];

        int c = smp[order-1] - 2*smp[order-2] +   smp[order-3];

        int e = smp[order-1] - 3*smp[order-2] + 3*smp[order-3] - smp[order-4];

        for (i = order; i < n; i += 2) {

            int b    = smp[i  ] - smp[i-1];

            int d    = b - a;

            int f    = d - c;

            res[i  ] = f - e;

            a        = smp[i+1] - smp[i  ];

            c        = a - b;

            e        = c - d;

            res[i+1] = e - f;

        }

    }

}

#define LPC1(x) {\

    int c = coefs[(x)-1];\

    p0   += c * s;\

    s     = smp[i-(x)+1];\

    p1   += c * s;\

}

static av_always_inline void encode_residual_lpc_unrolled(int32_t *res,

                                    const int32_t *smp, int n, int order,

                                    const int32_t *coefs, int shift, int big)

{

    int i;

    for (i = order; i < n; i += 2) {

        int s  = smp[i-order];

        int p0 = 0, p1 = 0;

        if (big) {

            switch (order) {

            case 32: LPC1(32)

            case 31: LPC1(31)

            case 30: LPC1(30)

            case 29: LPC1(29)

            case 28: LPC1(28)

            case 27: LPC1(27)

            case 26: LPC1(26)

            case 25: LPC1(25)

            case 24: LPC1(24)

            case 23: LPC1(23)

            case 22: LPC1(22)

            case 21: LPC1(21)

            case 20: LPC1(20)

            case 19: LPC1(19)

            case 18: LPC1(18)

            case 17: LPC1(17)

            case 16: LPC1(16)

            case 15: LPC1(15)

            case 14: LPC1(14)

            case 13: LPC1(13)

            case 12: LPC1(12)

            case 11: LPC1(11)

            case 10: LPC1(10)

            case  9: LPC1( 9)

                     LPC1( 8)

                     LPC1( 7)

                     LPC1( 6)

                     LPC1( 5)

                     LPC1( 4)

                     LPC1( 3)

                     LPC1( 2)

                     LPC1( 1)

            }

        } else {

            switch (order) {

            case  8: LPC1( 8)

            case  7: LPC1( 7)

            case  6: LPC1( 6)

            case  5: LPC1( 5)

            case  4: LPC1( 4)

            case  3: LPC1( 3)

            case  2: LPC1( 2)

            case  1: LPC1( 1)

            }

        }

        res[i  ] = smp[i  ] - (p0 >> shift);

        res[i+1] = smp[i+1] - (p1 >> shift);

    }

}

static void encode_residual_lpc(int32_t *res, const int32_t *smp, int n,

                                int order, const int32_t *coefs, int shift)

{

    int i;

    for (i = 0; i < order; i++)

        res[i] = smp[i];

#if CONFIG_SMALL

    for (i = order; i < n; i += 2) {

        int j;

        int s  = smp[i];

        int p0 = 0, p1 = 0;

        for (j = 0; j < order; j++) {

            int c = coefs[j];

            p1   += c * s;

            s     = smp[i-j-1];

            p0   += c * s;

        }

        res[i  ] = smp[i  ] - (p0 >> shift);

        res[i+1] = smp[i+1] - (p1 >> shift);

    }

#else

    switch (order) {

    case  1: encode_residual_lpc_unrolled(res, smp, n, 1, coefs, shift, 0); break;

    case  2: encode_residual_lpc_unrolled(res, smp, n, 2, coefs, shift, 0); break;

    case  3: encode_residual_lpc_unrolled(res, smp, n, 3, coefs, shift, 0); break;

    case  4: encode_residual_lpc_unrolled(res, smp, n, 4, coefs, shift, 0); break;

    case  5: encode_residual_lpc_unrolled(res, smp, n, 5, coefs, shift, 0); break;

    case  6: encode_residual_lpc_unrolled(res, smp, n, 6, coefs, shift, 0); break;

    case  7: encode_residual_lpc_unrolled(res, smp, n, 7, coefs, shift, 0); break;

    case  8: encode_residual_lpc_unrolled(res, smp, n, 8, coefs, shift, 0); break;

    default: encode_residual_lpc_unrolled(res, smp, n, order, coefs, shift, 1); break;

    }

#endif

}

static int encode_residual_ch(FlacEncodeContext *s, int ch)

{

    int i, n;

    int min_order, max_order, opt_order, omethod;

    FlacFrame *frame;

    FlacSubframe *sub;

    int32_t coefs[MAX_LPC_ORDER][MAX_LPC_ORDER];

    int shift[MAX_LPC_ORDER];

    int32_t *res, *smp;

    frame = &s->frame;

    sub   = &frame->subframes[ch];

    res   = sub->residual;

    smp   = sub->samples;

    n     = frame->blocksize;

    /* CONSTANT */

    for (i = 1; i < n; i++)

        if(smp[i] != smp[0])

            break;

    if (i == n) {

        sub->type = sub->type_code = FLAC_SUBFRAME_CONSTANT;

        res[0] = smp[0];

        return subframe_count_exact(s, sub, 0);

    }

    /* VERBATIM */

    if (frame->verbatim_only || n < 5) {

        sub->type = sub->type_code = FLAC_SUBFRAME_VERBATIM;

        memcpy(res, smp, n * sizeof(int32_t));

        return subframe_count_exact(s, sub, 0);

    }

    min_order  = s->options.min_prediction_order;

    max_order  = s->options.max_prediction_order;

    omethod    = s->options.prediction_order_method;

    /* FIXED */

    sub->type = FLAC_SUBFRAME_FIXED;

    if (s->options.lpc_type == AV_LPC_TYPE_NONE  ||

        s->options.lpc_type == AV_LPC_TYPE_FIXED || n <= max_order) {

        uint32_t bits[MAX_FIXED_ORDER+1];

        if (max_order > MAX_FIXED_ORDER)

            max_order = MAX_FIXED_ORDER;

        opt_order = 0;

        bits[0]   = UINT32_MAX;

        for (i = min_order; i <= max_order; i++) {

            encode_residual_fixed(res, smp, n, i);

            bits[i] = find_subframe_rice_params(s, sub, i);

            if (bits[i] < bits[opt_order])

                opt_order = i;

        }

        sub->order     = opt_order;

        sub->type_code = sub->type | sub->order;

        if (sub->order != max_order) {

            encode_residual_fixed(res, smp, n, sub->order);

            find_subframe_rice_params(s, sub, sub->order);

        }

        return subframe_count_exact(s, sub, sub->order);

    }

    /* LPC */

    sub->type = FLAC_SUBFRAME_LPC;

    opt_order = ff_lpc_calc_coefs(&s->lpc_ctx, smp, n, min_order, max_order,

                                  s->options.lpc_coeff_precision, coefs, shift, s->options.lpc_type,

                                  s->options.lpc_passes, omethod,

                                  MAX_LPC_SHIFT, 0);

    if (omethod == ORDER_METHOD_2LEVEL ||

        omethod == ORDER_METHOD_4LEVEL ||

        omethod == ORDER_METHOD_8LEVEL) {

        int levels = 1 << omethod;

        uint32_t bits[1 << ORDER_METHOD_8LEVEL];

        int order;

        int opt_index   = levels-1;

        opt_order       = max_order-1;

        bits[opt_index] = UINT32_MAX;

        for (i = levels-1; i >= 0; i--) {

            order = min_order + (((max_order-min_order+1) * (i+1)) / levels)-1;

            if (order < 0)

                order = 0;

            encode_residual_lpc(res, smp, n, order+1, coefs[order], shift[order]);

            bits[i] = find_subframe_rice_params(s, sub, order+1);

            if (bits[i] < bits[opt_index]) {

                opt_index = i;

                opt_order = order;

            }

        }

        opt_order++;

    } else if (omethod == ORDER_METHOD_SEARCH) {

        // brute-force optimal order search

        uint32_t bits[MAX_LPC_ORDER];

        opt_order = 0;

        bits[0]   = UINT32_MAX;

        for (i = min_order-1; i < max_order; i++) {

            encode_residual_lpc(res, smp, n, i+1, coefs[i], shift[i]);

            bits[i] = find_subframe_rice_params(s, sub, i+1);

            if (bits[i] < bits[opt_order])

                opt_order = i;

        }

        opt_order++;

    } else if (omethod == ORDER_METHOD_LOG) {

        uint32_t bits[MAX_LPC_ORDER];

        int step;

        opt_order = min_order - 1 + (max_order-min_order)/3;

        memset(bits, -1, sizeof(bits));

        for (step = 16; step; step >>= 1) {

            int last = opt_order;

            for (i = last-step; i <= last+step; i += step) {

                if (i < min_order-1 || i >= max_order || bits[i] < UINT32_MAX)

                    continue;

                encode_residual_lpc(res, smp, n, i+1, coefs[i], shift[i]);

                bits[i] = find_subframe_rice_params(s, sub, i+1);

                if (bits[i] < bits[opt_order])

                    opt_order = i;

            }

        }

        opt_order++;

    }

    sub->order     = opt_order;

    sub->type_code = sub->type | (sub->order-1);

    sub->shift     = shift[sub->order-1];

    for (i = 0; i < sub->order; i++)

        sub->coefs[i] = coefs[sub->order-1][i];

    encode_residual_lpc(res, smp, n, sub->order, sub->coefs, sub->shift);

    find_subframe_rice_params(s, sub, sub->order);

    return subframe_count_exact(s, sub, sub->order);

}

static int count_frame_header(FlacEncodeContext *s)

{

    uint8_t tmp;

    int count;

    /*

    <14> Sync code

    <1>  Reserved

    <1>  Blocking strategy

    <4>  Block size in inter-channel samples

    <4>  Sample rate

    <4>  Channel assignment

    <3>  Sample size in bits

    <1>  Reserved

    */

    count = 32;

    /* coded frame number */

    PUT_UTF8(s->frame_count, tmp, count += 8;)

    /* explicit block size */

    if (s->frame.bs_code[0] == 6)

        count += 8;

    else if (s->frame.bs_code[0] == 7)

        count += 16;

    /* explicit sample rate */

    count += ((s->sr_code[0] == 12) + (s->sr_code[0] > 12)) * 8;

    /* frame header CRC-8 */

    count += 8;

    return count;

}

static int encode_frame(FlacEncodeContext *s)

{

    int ch, count;

    count = count_frame_header(s);

    for (ch = 0; ch < s->channels; ch++)

        count += encode_residual_ch(s, ch);

    count += (8 - (count & 7)) & 7; // byte alignment

    count += 16;                    // CRC-16

    return count >> 3;

}

static int estimate_stereo_mode(int32_t *left_ch, int32_t *right_ch, int n)

{

    int i, best;

    int32_t lt, rt;

    uint64_t sum[4];

    uint64_t score[4];

    int k;

    /* calculate sum of 2nd order residual for each channel */

    sum[0] = sum[1] = sum[2] = sum[3] = 0;

    for (i = 2; i < n; i++) {

        lt = left_ch[i]  - 2*left_ch[i-1]  + left_ch[i-2];

        rt = right_ch[i] - 2*right_ch[i-1] + right_ch[i-2];

        sum[2] += FFABS((lt + rt) >> 1);

        sum[3] += FFABS(lt - rt);

        sum[0] += FFABS(lt);

        sum[1] += FFABS(rt);

    }

    /* estimate bit counts */

    for (i = 0; i < 4; i++) {

        k      = find_optimal_param(2 * sum[i], n);

        sum[i] = rice_encode_count( 2 * sum[i], n, k);

    }

    /* calculate score for each mode */

    score[0] = sum[0] + sum[1];

    score[1] = sum[0] + sum[3];

    score[2] = sum[1] + sum[3];

    score[3] = sum[2] + sum[3];

    /* return mode with lowest score */

    best = 0;

    for (i = 1; i < 4; i++)

        if (score[i] < score[best])

            best = i;

    if (best == 0) {

        return FLAC_CHMODE_INDEPENDENT;

    } else if (best == 1) {

        return FLAC_CHMODE_LEFT_SIDE;

    } else if (best == 2) {

        return FLAC_CHMODE_RIGHT_SIDE;

    } else {

        return FLAC_CHMODE_MID_SIDE;

    }

}

/**

 * Perform stereo channel decorrelation.

 */

static void channel_decorrelation(FlacEncodeContext *s)

{

    FlacFrame *frame;

    int32_t *left, *right;

    int i, n;

    frame = &s->frame;

    n     = frame->blocksize;

    left  = frame->subframes[0].samples;

    right = frame->subframes[1].samples;

    if (s->channels != 2) {

        frame->ch_mode = FLAC_CHMODE_INDEPENDENT;

        return;

    }

    frame->ch_mode = estimate_stereo_mode(left, right, n);

    /* perform decorrelation and adjust bits-per-sample */

    if (frame->ch_mode == FLAC_CHMODE_INDEPENDENT)

        return;

    if (frame->ch_mode == FLAC_CHMODE_MID_SIDE) {

        int32_t tmp;

        for (i = 0; i < n; i++) {

            tmp      = left[i];

            left[i]  = (tmp + right[i]) >> 1;

            right[i] =  tmp - right[i];

        }

        frame->subframes[1].obits++;

    } else if (frame->ch_mode == FLAC_CHMODE_LEFT_SIDE) {

        for (i = 0; i < n; i++)

            right[i] = left[i] - right[i];

        frame->subframes[1].obits++;

    } else {

        for (i = 0; i < n; i++)

            left[i] -= right[i];

        frame->subframes[0].obits++;

    }

}

static void write_utf8(PutBitContext *pb, uint32_t val)

{

    uint8_t tmp;

    PUT_UTF8(val, tmp, put_bits(pb, 8, tmp);)

}

static void write_frame_header(FlacEncodeContext *s)

{

    FlacFrame *frame;

    int crc;

    frame = &s->frame;

    put_bits(&s->pb, 16, 0xFFF8);

    put_bits(&s->pb, 4, frame->bs_code[0]);

    put_bits(&s->pb, 4, s->sr_code[0]);

    if (frame->ch_mode == FLAC_CHMODE_INDEPENDENT)

        put_bits(&s->pb, 4, s->channels-1);

    else

        put_bits(&s->pb, 4, frame->ch_mode);

    put_bits(&s->pb, 3, 4); /* bits-per-sample code */

    put_bits(&s->pb, 1, 0);

    write_utf8(&s->pb, s->frame_count);

    if (frame->bs_code[0] == 6)

        put_bits(&s->pb, 8, frame->bs_code[1]);

    else if (frame->bs_code[0] == 7)

        put_bits(&s->pb, 16, frame->bs_code[1]);

    if (s->sr_code[0] == 12)

        put_bits(&s->pb, 8, s->sr_code[1]);

    else if (s->sr_code[0] > 12)

        put_bits(&s->pb, 16, s->sr_code[1]);

    flush_put_bits(&s->pb);

    crc = av_crc(av_crc_get_table(AV_CRC_8_ATM), 0, s->pb.buf,

                 put_bits_count(&s->pb) >> 3);

    put_bits(&s->pb, 8, crc);

}

static void write_subframes(FlacEncodeContext *s)

{

    int ch;

    for (ch = 0; ch < s->channels; ch++) {

        FlacSubframe *sub = &s->frame.subframes[ch];

        int i, p, porder, psize;

        int32_t *part_end;

        int32_t *res       =  sub->residual;

        int32_t *frame_end = &sub->residual[s->frame.blocksize];

        /* subframe header */

        put_bits(&s->pb, 1, 0);

        put_bits(&s->pb, 6, sub->type_code);

        put_bits(&s->pb, 1, 0); /* no wasted bits */

        /* subframe */

        if (sub->type == FLAC_SUBFRAME_CONSTANT) {

            put_sbits(&s->pb, sub->obits, res[0]);

        } else if (sub->type == FLAC_SUBFRAME_VERBATIM) {

            while (res < frame_end)

                put_sbits(&s->pb, sub->obits, *res++);

        } else {

            /* warm-up samples */

            for (i = 0; i < sub->order; i++)

                put_sbits(&s->pb, sub->obits, *res++);

            /* LPC coefficients */

            if (sub->type == FLAC_SUBFRAME_LPC) {

                int cbits = s->options.lpc_coeff_precision;

                put_bits( &s->pb, 4, cbits-1);

                put_sbits(&s->pb, 5, sub->shift);

                for (i = 0; i < sub->order; i++)

                    put_sbits(&s->pb, cbits, sub->coefs[i]);

            }

            /* rice-encoded block */

            put_bits(&s->pb, 2, 0);

            /* partition order */

            porder  = sub->rc.porder;

            psize   = s->frame.blocksize >> porder;

            put_bits(&s->pb, 4, porder);

            /* residual */

            part_end  = &sub->residual[psize];

            for (p = 0; p < 1 << porder; p++) {

                int k = sub->rc.params[p];

                put_bits(&s->pb, 4, k);

                while (res < part_end)

                    set_sr_golomb_flac(&s->pb, *res++, k, INT32_MAX, 0);

                part_end = FFMIN(frame_end, part_end + psize);

            }

        }

    }

}

static void write_frame_footer(FlacEncodeContext *s)

{

    int crc;

    flush_put_bits(&s->pb);

    crc = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, s->pb.buf,

                            put_bits_count(&s->pb)>>3));

    put_bits(&s->pb, 16, crc);

    flush_put_bits(&s->pb);

}

static int write_frame(FlacEncodeContext *s, uint8_t *frame, int buf_size)

{

    init_put_bits(&s->pb, frame, buf_size);

    write_frame_header(s);

    write_subframes(s);

    write_frame_footer(s);

    return put_bits_count(&s->pb) >> 3;

}

static void update_md5_sum(FlacEncodeContext *s, const int16_t *samples)

{

#if HAVE_BIGENDIAN

    int i;

    for (i = 0; i < s->frame.blocksize * s->channels; i++) {

        int16_t smp = av_le2ne16(samples[i]);

        av_md5_update(s->md5ctx, (uint8_t *)&smp, 2);

    }

#else

    av_md5_update(s->md5ctx, (const uint8_t *)samples, s->frame.blocksize*s->channels*2);

#endif

}

static int flac_encode_frame(AVCodecContext *avctx, uint8_t *frame,

                             int buf_size, void *data)

{

    FlacEncodeContext *s;

    const int16_t *samples = data;

    int frame_bytes, out_bytes;

    s = avctx->priv_data;

    /* when the last block is reached, update the header in extradata */

    if (!data) {

        s->max_framesize = s->max_encoded_framesize;

        av_md5_final(s->md5ctx, s->md5sum);

        write_streaminfo(s, avctx->extradata);

        return 0;

    }

    /* change max_framesize for small final frame */

    if (avctx->frame_size < s->frame.blocksize) {

        s->max_framesize = ff_flac_get_max_frame_size(avctx->frame_size,

                                                      s->channels, 16);

    }

    init_frame(s);

    copy_samples(s, samples);

    channel_decorrelation(s);

    frame_bytes = encode_frame(s);

    /* fallback to verbatim mode if the compressed frame is larger than it

       would be if encoded uncompressed. */

    if (frame_bytes > s->max_framesize) {

        s->frame.verbatim_only = 1;

        frame_bytes = encode_frame(s);

    }

    if (buf_size < frame_bytes) {

        av_log(avctx, AV_LOG_ERROR, "output buffer too small\n");

        return 0;

    }

    out_bytes = write_frame(s, frame, buf_size);

    s->frame_count++;

    avctx->coded_frame->pts = s->sample_count;

    s->sample_count += avctx->frame_size;

    update_md5_sum(s, samples);

    if (out_bytes > s->max_encoded_framesize)